Final answer:
Cytoskeletal elements such as actin microfilaments and microtubules are unique to eukaryotic cells, and not found in prokaryotic bacterial or archaean cells. Hence, the correct answer is C. eukaryotes.
Step-by-step explanation:
Cytoskeletal elements are found in eukaryotic cells, which include all members of the domain Eukarya. However, it is not correct to say that similar structures are found within bacterial prokaryotic cells or archaean prokaryotic cells, as they do not possess the same cytoskeletal elements like actin microfilaments and microtubules. While prokaryotes have some structural proteins that can be likened to a cytoskeleton, these are fundamentally different from the cytoskeletal elements found in eukaryotes. Therefore, the correct answer to which organisms contain cytoskeletal elements is C. eukaryotes.